Sirius Minerals has come under pressure on new doubts about its plans to develop a potash mine in the North York moors national park.

The Park Authority has issued a report which - while it makes no recommendation - said the project would be more harmful than beneficial to the local area. The economic benefits and compensation did not outweigh the damage that would be caused, it said:

Officers conclude that the policy conflict with the Development Plan and national policy is such that the proposal does not represent Exceptional Circumstances, which is the highest bar that planning policy requires. It is therefore considered that the economic benefits and extent of the mitigation/compensation offered through planning obligations do not outweigh the extent of the harm and clear conflict with the development plan.

The report will be presented to a planning committee meeting on 30 June, when a decision whether to go ahead or not will be made.

Sirius shares are currently 3.75p or 17% lower at 17.75p, but the company’s managing director Chris Fraser said:

We believe the case for approval is very strong because the project represents a once in a generation opportunity.

Analysts at RFC Ambrian said:

While the report makes no recommendation, and nor was it designed to, its conclusions were not exactly helpful for Sirius.

The report concluded that it does not believe the development “represents exceptional circumstances”. This is very significant as it is key for receiving planning consent within a National Park.

What needs to be remembered is that this report’s conclusions are solely from the view point of the Park Authority. Its only interest is the park. There will obviously be a conflict between what the park thinks and the wider interests of North Yorkshire as an economic and social entity. The final decision on the project will be made by a Special Planning Committee; this will meet on 30 June, so there’s not long to go now.

And Liberum continues to believe the project will get the go-ahead:

Consistent with previous guidance [the authority] has offered a neutral recommendation. As we’ve noted, a neutral recommendation feels most likely to result in a positive vote given the majority of the Park members represent political organisations who’ve previously expressed support for the project.

However, today’s release also included some commentary suggesting that the planning committee doesn’t feel the project represents the exceptional circumstances required for development.

For us, there is no change to our view that approval is the most likely outcome as we’ve previously noted that the planning committee was likely to place more weight on the park’s preservation and its official recommendation remains neutral.